HISTORICAL. 25 



"Overgrazing for an extended period will leave 'earmarks,' which usually 

 will be recognized. To recognize current overgrazing at the time of examina- 

 tion on a range previously not overgrazed is difficult and yet important in 

 order to make timely adjustment. The following obvious earmarks are the 

 most rehable indicators of overgrazing prior to the year of examination: 



" The predominance of weeds and grasses such as knotweed (Polygonum spp.), 

 tarweed (Madia spp.), mustard (Sophia incisa), annual brome grasses (Bromus 

 hordeaceus, brizaeformis, tectorum), and fescues (Festuca megalura, micro- 

 stachys, confusa), with a dense stand of such species and lack of variety in 

 species. This condition is a severe stage of overgrazing such as occurs around 

 sheep bedding grounds which have been used for long periods each year for 

 several years in succession. 



" The predominance of plants which have Utile or no value for any class of stock, 

 such as sneezeweed (Dugaldia hoopesii), niggerhead (Rudbeckia ocddentalis), 

 yellowweed (Senecio eremophilus) , snakeweed (Gutierrezia sarothrae) and gum- 

 weed (Grindelia squarrosa). These and similar plants frequently occur in 

 abundance over large areas of range and indicate that the range needs careful 

 management to give better forage plants a chance to grow. 



" The presence of dead and partly dead stumps of shrubs, such as snowberry 

 (Symphoricarpos oreophilus), currant (Ribes spp.), willow (Salix spp.), service 

 berry (Amelanchier spp.), birch-leaf mahogany (Cercocarpu^ montanus), and 

 Gambel oak (Quercus gambellii). This condition usually indicates that the 

 most palatable grasses and weeds have been overgrazed. There may be some 

 exceptions to this, as in the case of drawfed willows on ranges where grasses 

 predominate above timber line. Sheep sometimes kill the willows before the 

 grasses are overgrazed. 



^^ Noticeable damage to tree reproduction, especially to western yellow-pine 

 (Pinus ponderosa) reproduction on sheep range and aspen (Populus tremu- 

 loides) reproduction on cattle range. Lack of aspen reproduction on a weed 

 sheep range indicates overgrazing, provided the natural conditions are favor- 

 able to aspen reproduction. On a sheep range where grass predominates 

 severe injury to western yellow-pine or aspen reproduction may indicate that 

 the range is not well suited to sheep. 



"The earmarks described are, perhaps, more typical of overgrazed sheep 

 range than of overgrazed cattle range, but the general appearance of the two 

 does, not differ greatly when overgrazing reaches a stage to be recognized by 

 one or more of these earmarks. The main differences are in the species of 

 plants indicating the overgrazing. Weeds eaten by sheep are often found in 

 abundance on overgrazed cattle range; coarse grasses palatable to cattle are 

 often abundant on overgrazed sheep range. This fact has given rise to the 

 use of the term 'class overgrazing.' " 



Sarvis, 1919. ^The first adequate intensive experiments in grazing have 

 been carried on by Sarvis (1919) at Mandan, North Dakota, since 1916, and 

 at Ardmore, South Dakota, since 1918. These have dealt primarily with 

 carrying capacity and rotation grazing, though a number of related problems 

 have been taken into account, such as rate of growth, effect of mowing, etc. 

 The experiments are based upon actual grazing tests to determine the present 

 carrying capacity of a particular type and the optimum utilization resulting 

 from rotation At Mandan, for example, the carrying capacity tests comprise 

 four fields of 30, 50, 70 and 100 acres respectively, each grazed by 10 animals 

 of the same age and class. These are weighed at frequent intervals and the 

 carrying capacity expressed in terms of pounds gained in weight. There are 



